The present invention relates to an exposure apparatus that is configured to expose a pattern on an original onto a substrate. The present invention is preferably applied to an exposure apparatus which performs an exposure using short wavelength light such as EUV light (0.5 to 50 nm) under a high-vacuum atmosphere.
In an optical lithography technology for manufacturing semiconductors, the wavelength of the exposure light has been shortened from an i-line or a g-line to a KrF excimer laser or an ArF excimer laser in accordance with the miniaturization of the semiconductors. If the wavelength of the exposure light has been shortened, a finer mask pattern can be exposed onto a wafer.
Recently, an EUV lithography using extreme ultraviolet light (EUV light: 13 to 20 nm) whose wavelength is shorter than that of ultraviolet light has attracted attention. Japanese Patent Laid-Open No. 2003-45782 discloses a reduced projection exposure apparatus using the EUV light as an exposure light.
A problem common to conventional exposure apparatuses using an i-line, a KrF excimer laser, an ArF excimer laser, or an EUV is that a defect is generated by a particle adhering to the original. In the exposure apparatus using the i-line, the g-line, the KrF excimer laser, and the ArF excimer laser, the adhesion of the particle to the original was avoided by placing a transparent protection film called a pellicle at a distance of several millimeters from the original.
However, in the EUV exposure apparatus to which the present invention applies, there is no pellicle transparent for the EUV light. If the absorption of the EUV light is allowed to some extent, the pellicle can be made of a material having a high-transmittance. However, when a required transmittance of the EUV light should be obtained, the thickness of the pellicle needs to be around several tens of nanometers. It is difficult for the thin film whose thickness is several tens of nanometers to withstand the harsh environment such as heat generated by the absorption of the EUV light.
Therefore, the original in the EUV exposure apparatus have to be pellicleless. If the particle is generated in the exposure apparatus, the adhesion of the particle to the original is concerned.
Japanese Patent Laid-Open Nos. 2006-32957 and 2006-120776 disclose a technology for preventing a contaminant such as a particle from adhering to an optical element or a substrate in the exposure apparatus.
However, in the technology disclosed in Japanese Patent Laid-Open No. 2006-32957, a charged body is provided on a projection system or a substrate table which should be protected from the contaminant, and the electric field is formed between the charged body and the projection system or the charged body and the substrate table. In this configuration, the contaminant charged with the same polarity as that of the charged body is not attracted to the charged body, but is attracted to the projection system or the substrate table. Therefore, an intended effect can not be obtained.
In a technology disclosed in Japanese Patent Laid-Open No. 2006-120776, an electrode is buried in an electrostatic chuck that holds the original. In this case, the particle is attracted to the electrostatic chuck, and the adherence of the particle to the absorption surface of the original is concerned. If the particle is adhered to the absorption surface of the original, the surface accuracy of the original may be influenced.